On a recent morning, Ingrid Feustel and Ed Trommelen donned rubber boots, grabbed nets and collection buckets, and splashed their way into a tributary of the Red Clay Creek in search of stoneflies.

The duo are spending the summer conducting a macroinvertebrate survey as Stream Watch interns for the Delaware Nature Society.

As Feustel set out sampling jars, Trommelen kicked up pebbles with the toe of his boot, then dragged the net over the churned-up water. “I’ve got some stoneflies,” said Trommelen, after a glance inside the net.

Most people would probably only notice leaves, twigs and pebbles but Trommelen quickly identified the stoneflies, even though they’re itty-bitty (one-half to 1 1/2 inches long as adults and even smaller as juveniles.)

The interns collected stoneflies throughout the morning, making note of how many were in each sample, as well as any other macroinvertebrates — such as mayflies, caddisflies and worms — that they found. While it’s certainly fun to splash around a sun-dappled creek on a June day, why would the Delaware Nature Society care how many stoneflies are in local creeks?